concerning shredder blades-Any metallurgists out there?Maybe a welder can answer this

[Kyle_in_Tex]

I was told by a friend that some folks would weld a piece of tool steel to the front edge of their shredder blades for longer life.

I'm a machinist by trade, but not a "weld and fix it" repair type machinist.

Obviously I would be worried about it breaking off and go slinging. But if you properly prepped with weld bevels both the blade and the tool steel, then pre-heated, welded then post heated in an oven, How much do you think the quality of better steel would work?

The trick would be to keep the dis similar tool steel from cracking. Also, if you didn't quick cool it after welding to really harden it, it would stay relatively soft but still much tougher than the original blade. Maybe I need to re-think this and use a different tough metal like 17-4 Stainless or something else.

Comments?

 

[EddieWalker]

While I'm a big fan of modifying things to make them better, I've also learned over the years that it rarely works out like I had planned. Considering the cost of buying new blades to what you might gain by modifying them and the time and money it will take to accomplish this. Then comparing how well stock blades work compared to the modified ones and if the modified ones will even cut better or last longer, along with balancing them, makes it tough to see the advantage.

Eddie

 

[tmc_31]

Hey Kyle,

I would be concerned that the hard (brittle) tool steel hitting rocks and other hidden hazards in the grass would fracture the steel. I have often wondered about welding hardface or something similar on the leading edges of shredder blades but I haven't tried it yet.

Tim

 

[dusty3030]

While I'm a big fan of modifying things to make them better, I've also learned over the years that it rarely works out like I had planned. Considering the cost of buying new blades to what you might gain by modifying them and the time and money it will take to accomplish this. Then comparing how well stock blades work compared to the modified ones and if the modified ones will even cut better or last longer, along with balancing them, makes it tough to see the advantage. Eddie

Agree -

 

[CalG]

The "big boys" in the chipper shredder business (Industrial, think shredding tires or entire automobiles) use "tipped" blades of one sort or another.

A set of swinging blades for tractor driven garden shredders might cost $100. That's usually four corners of service life.
Time and trouble to put tips on by brazing (can't recommend welding at all) might be $500. Might be double that (my shredder has 48 swinging blades, I don't think I would tip each one for $10, but...?)

And rocks will still get them ;-)

Hard facing rod and a bench grinder would be a more economical approach.

 

[crazyal]

I wouldn't mess with the blade. Most likely it's not mild steel to begin with so once you weld it (add heat) you'll most likely change it's properties. You could loose any tempering that it had and actually make it weaker.

 

[RedNeckGeek]

I was told by a friend that some folks would weld a piece of tool steel to the front edge of their shredder blades for longer life.
[SNIP]
Obviously I would be worried about it breaking off and go slinging. But if you properly prepped with weld bevels both the blade and the tool steel, then pre-heated, welded then post heated in an oven, How much do you think the quality of better steel would work?

Your thinking is correct: It's pretty straight forward to weld a hardenable steel to the blade to form a longer lasting edge, but you do need to worry about the hard, brittle material that will form in the weld heat affected zone of the tool steel. Pre-heat, maximum interpass temperature, and post weld heat treat would all depend on the steels chosen for the application, but with the right choices, your strategy will result in a more durable cutting edge that won't break off the carrier.

The manufacturers must walk a balance between affordability and manufactureability, but if you can do the work yourself for free you might not worry so much how long it'll take you. The ASM's Metals Handbooks will tell you all you need to know about welding procedure and post weld heat treat to get a hard but durable edge, but you'll still need a heat source, some way of measuring temperature accurately, the ability to hold a given temperature for a certain amount of time, and a quenching setup with the correct medium to achieve the recommended cooling rate. Likely you'll also need to temper the weldment after heat treatment using the same setup. Once you've got something you think will work, how do you test it? A metallurgical lab could run micro hardness traverses across the weld zone to verify there were no hard brittle spots, and tensile test machines can verify that failure would be through ductile fracture. Any big company that deals with alloy steels will have all that, and I've worked as a welding engineer at a few of them. More than once "government jobs" found their way in through the door, but since I've retired I wouldn't consider my Lincoln and Miller welders, oxy-acetylene outfit, Harbor Freight IR temperature probe, and a bucket of water or used motor oil up to the task you describe.

Even if it were, and as others have mentioned, what is your time worth? And what happens to that beautiful edge the first time you hit a rock or piece of metal?

Interesting project, but if it were me I think I'd just stick with what came on the machine and be happy to avoid all the welding and fussing by just replacing or grinding the blade when it becomes dull.

 

[Baby Grand]

I'm assuming that by shredder you mean a brush hog type of blade. Throwing a blade on a shredder is not something I want to be around for. If you know the metallurgy of the production shredder blades and can be certain that the hard tipped blades have equal or better characteristics (ductility & fracture toughness), then I'd say go for it. Otherwise, I'd leave well enough alone - the cost of failure can be very high on this one.

 

[Ken45101]

My gosh, what are you cutting that you are worried about blade wear?

I only sharpen my blades every 5 years or so! (They are not supposed to be real sharp.) My 72" brush mower is 15 years old and while it most handles pastures, it also gets into the woods clearing heavy brush and saplings. (Stuff big enough that I back over, I won't drive the tractor forward over it.) And the brush cutter on the skid steer? I recently took down a 6" tree with it.

No, I certainly would not take the risk welding or brazing the blades on a brush cutter.

Don't forget, if your welds are not identical, you will unbalance the unit.

 

[Kyle_in_Tex]

I understand the KISS principle (Keep it stock stupid) and usually abide by it. I just also know that the stamped steel blades sold aren't the absolute best quality alloy available.

I do have rocks. Up to potato size pieces of flint and my blades end up looking like hammered dog crap. That being said, it would be a total government project (free labor and machine time).

The possibilities are endless. I could dovetail the blade and the hard metal with a close fit, slide the piece of alloy in place and then weld. I just don't have a real big oven where I work. The piece I'm considering would weigh less than a pound or two. This would be about the same weight as the rocks I hit.

Sharp blades just leave such a better cut than a dull 1/2" or 3/4" fully rounded dull blade. If you are cutting saplings, leave them dull, but for a nice clean cut, give me a sharp blade anyday. It makes a BIG difference in the HP required to cut down your field, so fuel savings is a return factor.

Thanks for the replies.